1. Field of Invention
This invention concerns maintaining the temperature and relative humidity of the air within an image forming device.
2. Description of Related Art
This invention is related to co-pending application, Ser. No. 09/714,973, entitled xe2x80x9cAmbient Atmospheric Pressure Compensation Controller for Pressurized Copy Device,xe2x80x9d filed May 1, 2000, now U.S. Pat. No. 6,334,033, which is incorporated herein by reference in its entirety.
Certain image forming devices, such as, for example, photocopiers, require a temperature controlled environment for increased operational efficiency. However, introducing air conditioning to such devices presents a potential problem in that water vapor in the conditioned air which is used to control the temperature of the device may condense onto component parts of the device.
In U.S. Pat. No. 4,367,036, a temperature and humidity compensating device uses a temperature sensor to detect the temperature of the photosensitive member. A control means is used to control a source of heat located inside the photosensitive member. The heat source is used to keep the temperature of the photosensitive member above ambient temperature to prevent moisture from condensing on, and being absorbed by, the photosensitive member.
In U.S. Pat. No. 5,530,523, sensors are provided near the photosensitive member to measure the temperature and humidity near the outer surface of the photosensitive member. A means for calculating a water vapor density is associated with the measured temperature and humidity. A control unit compares a pre-selected water vapor density with the calculated water vapor density. A control unit activates a heater inside the photosensitive member to prevent forming of dew on the photosensitive member based on the comparison.
In U.S. Pat. No. 4,982,225, an image forming apparatus form an image of high quality even in a highly humid atmosphere. Humidity in the apparatus is detected and a heating means is activated by a controller connected to the humidity detecting means. The microcapsule paper used in the device is heated when the humidity is at or below a certain value.
U.S. Pat. No. 5,144,366 discloses a cooling system for an image forming machine that includes a single temperature sensor to detect the temperature inside of the machine and to control the operation of a cooling fan. The cooling fan is used to lower the temperature inside the machine in accordance with the detected temperature and the number of sheets to be copied.
U.S. Pat. No. 5,206,754 discloses a moisture condensation prevention structure for a laser scanning optical system in an electro-photographic image forming device that includes a device for preventing air from circulating in the laser beam optical assembly casing by separating the casing into different compartments.
Introducing air conditioning presents a potential problem, in that condensation can accumulate on critical machine parts.
None of these devices discloses the unique methods and devices employed by this invention to achieve moisture condensation control.
This invention provides methods and apparatus that control the properties of air supplied to at least a portion of an image forming device to avoid a dew point condition in that portion of the image forming device.
This invention separately provides systems and methods that control the air temperature and relative humidity to avoid dew point conditions in at least a portion of an image forming device.
Air which circulates throughout an image forming device may contain high relative humidity. The water vapor contained in such air may condense on various elements of the image forming device causing unwanted effects on optical elements, image transfer elements or materials, and on other elements in the image forming device.
In a first exemplary embodiment of the systems and methods according to this invention, an environmental control unit provides air to a xerographic portion of the image forming device to maintain that portion at a desired temperature, relative humidity and pressure. One or more of the temperature, relative humidity and pressure are selected to substantially reduce the likelihood that water vapor will condense on that portion of the image forming device.
In various exemplary embodiments, the environmental control unit operates in a semi-closed mode. In the semi-closed mode, air is cycled and recycled through the portion, while additional air is added to maintain a desired pressure in that portion.
In a second exemplary embodiment of the systems and methods according to this invention, ambient air temperature, and the temperature and relative humidity in a portion of the image forming device are determined, along with a saturation temperature and a desired set point or control reference temperature of operation. In a first mode of operation of the second exemplary embodiment, the system air will be conditioned using an air conditioner. In this first mode, the air re-circulates in a closed loop through the air conditioner and at least that portion of the image forming device. In a second mode of operation of the second exemplary embodiment, the system air will be conditioned using only the blower, and will circulate in the closed loop.
In a third mode of operation of the second exemplary embodiment, the system air will be conditioned using the air conditioner. In this third mode, the air circulates through the air conditioner and at least that portion of the image forming device in a loop open to the ambient atmosphere. In a fourth mode of operation of the second exemplary embodiment, the system air will be conditioned using only the blower, and will circulate in the open loop condition.
In any mode of operation, an air diffuser embodiment is provided to reduce the amount of toner which is picked up from toner development units by the air flowing throughout the xerographic unit to reduce the amount of toner picked up by the air flow thereby reducing the amount of airborne toner on developed and fixed images.
These and other features of this invention are described in, or are present from, the following detailed description of the various exemplary embodiments of the dew point control methods and apparatus according to this invention.